1. Field of the Invention
The present invention relates to a color cathode ray tube. More particularly, it relates to a color cathode ray tube having a slim neck portion and a stem with an electron gun optimally joined to the neck portion.
2. Discussion of Related Art
Generally, a cathode ray tube of FIG. 1 includes a fluorescent layer 20, a panel 10 having a shadow mask 30 spaced a given distance away from fluorescent layer 20, a funnel 40 having a slim neck portion 40a at the rear and secured to panel 10, an electron gun 50 housed in the neck portion 40a and emitting an electron beam 70 to the fluorescent layer 20, and a stem 60 sealed to neck portion 40a and executing the exhaust stroke through an exhaust pipe 60a provided to the stem 60.
There is a deflection yoke 80 on the outer circumference of neck portion 40a of the cathode ray tube for deflecting an electron beam 70 emitted from electron gun 50. When a heater in a cathode (not shown) on stem 60 of electron gun 50 emits, an oxide compound, applied to the upper surface of a cathode, emits electrons. The electrons emitted from the oxide compound of the cathode pass through the respective electrodes and form an electron beam 70 of required characteristics. The electron beam 70 is deflected by a magnetic field created by deflection yoke 80, and passes through shadow mask 30 and hits on fluorescent layer 20 applied to the inside of panel 10 so that fluorescent layer 20 emits light to represent an image.
The cathode ray tube maintains a vacuum condition to smoothly perform the above operation, and stem 60 with a plurality of stem pins 90 for supplying power to electron gun 50 and exhaust pipe 60a for exhaust is assembled to neck portion 40a. The interior of the cathode ray tube is evacuated via exhaust pipe 60a, and thereafter exhaust pipe 60a is melted and sealed to maintain a vacuum condition.
The smaller the diameter of neck portion 40a becomes, the smaller the electric current that flows across the coil constituting deflection yoke 80. The deflection yoke 80 creates a magnetic field when electron gun 50 operates in order that the electron beam emitted from electron gun 50""s oxide compound approaches fluorescent layer 20 applied to panel 10, Much research and developments have been made to minimize the diameter of neck portion 4a, but there is a limit to the amount of diameter reduction of a neck portion 40a. 
First, as the diameter of neck portion 40a is reduced, the resolution of the electron gun is degraded yet, a high-performance electron gun of optimum design is desirable. Astigmatism that may occur by the deflection yoke by supplying focus voltages divided into two, thus compensating the resolution degradation around the screen peripheral part and optimizing a main lens. This enhances the uniformity of spots and assures high-performance of the electron gun. According to the techniques of dividing the focus voltage into two, the focus voltage is applied to a single stem pin to be divided into more than two voltages by a resistor mounted on the electron gun of the neck portion, and each focus voltage is applied through two focus voltage applying pins.
Second, as the diameter of neck portion 40a is reduced, the shape and size of the stem with metal pins for supplying one or two focus voltages and the required power to the electron gun need to be more precisely set, If not, a proper seal is not formed at the joint of stem 6 and neck portion 40a. Even if the seal is properly formed, cracks may form such that the interior of the cathode ray tube is not in a perfect vacuum state and causes poor internal voltage characteristics due to the improper sealing.
In stem 6, metallic stem pins 9 are equidistantly disposed in a circular formation on the middle of stem 6 to provide the proper insulation, and the diameter of the circular information formed by the stem pins 9 is about 15.24 mm or 12.00 mm. A glass projection 6b is integrally formed with stem 6 around stem pins 9 in order to increase the strength and insulating characteristics the metallic stem pins 9. When employing a slim neck portion 4a, stem 6 having a pin circle of 15.24 mm in diameter has a larger outer diameter than the neck portion 4a""s inner diameter such that glass projection 6b comes in contact with neck portion 4a to cause cracking thereof or result in poor internal voltage characteristics.
Stem 6 having a circular information of 12.0 mm in diameter has an outer diameter that is much smaller than the inner diameter of neck portion 4a to this not form a proper seal. Even if the seal is formed; the sealed portion is too this, which is susceptible to cracking when forming a vacuum within the cathode ray tube.
Accordingly, the present invention is directed to a color cathode ray tube that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a cathode ray tube with a slim neck portion and a stem. Each having an optimum size for sealing.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the present invention provides a color cathode ray tube having a panel to which a fluorescent layer is applied, a slim neck portion receiving an electron gun therein, a funnel joined to the panel, and a stem with the electron gun sealed to the neck portion, wherein if an inner diameter of the neck portion and an outer diameter of the stem equal a and f, respectively, an interval between the neck portion""s inner diameter a and the stem""s outer circumference meets the condition of 0.2 mmxe2x89xa6(axe2x88x92f)/2xe2x89xa630.0 mm, and the neck portion""s outer diameter equals 23.0 mm to 28.5 mm.
According to another aspect of the present invention, in a color cathode ray tube having a panel to which a fluorescent layer is applied, a slim neck portion with an electron gun, therein a funnel joined to the panel, and a stem with the electron gun sealed to the neck portion, if an inner diameter of the neck portion and an outer diameter of the stem equal a and f, respectively, an interval between the neck portion""s inner diameter and the stem""s outer circumference meets the condition of 0.85 a mmxe2x89xa6f xe2x89xa60.98 a mm.
According to still another aspect of the present invention, in a color cathode ray tube having a panel to which a fluorescent layer is applied, a slim neck portion with an electron gun, therein a funnel joined to the panel, and a stem with the electron gun sealed to the neck portion, if an outer diameter of the neck portion and a thickness of the neck portion equal b and t, respectively, they meet the condition of 0.08 b mmxe2x89xa6txe2x89xa60.1 b mm, and an outer diameter of the neck portion is 23.0 to 28.5 mm.
According to a further aspect of the present invention, in a color cathode ray tube having a panel to which a fluorescent layer is applied, a slim neck portion receiving an electron gun, therein, a funnel joined to the panel, and a stem with the electron gun sealed to the neck portion, if a thickness of the neck portion and a thickness of the stem equal t and T, respectively, they meet the condition of 0.8 tmmxe2x89xa6Txe2x89xa61.4 tmm.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.